Suchergebnisse

AbstractThis paper reviews the approaches used to deal with the interpretation of measurements reported as 'less than' a stated reporting limit. The principal current methodologies are examined and their shortcomings discussed. Recent key papers on the subject are summarised. It is concluded that lack of easy‐to‐use alternative methods have led to the continued use of substitution methods that are acknowledged to be biased. With the aim of promoting a more technically sound approach to dealing with 'less than' data, a supplementary spreadsheet tool is supplied to provide the reader with ready introductory access to a simple way to apply maximum likelihood methods. Recommendations and simple guidelines for better practice are provided.

AbstractThe majority of drinking water supply zones in the United Kingdom are currently dosed with phosphate in order to meet the drinking water quality standards for lead. Consequent reductions in other metals released from domestic plumbing might be expected. Lead, copper, zinc and nickel concentrations in the tap water of supply zones and in effluents from related sewage works were examined to assess reductions in the concentrations of these metals associated with the dosing of orthophosphate. This paper provides an analysis of the impact of phosphate dosing of drinking water on the metal concentrations in drinking water and sewage work effluents and the potential impacts in relation to the Water Framework Directive. Phosphate treatment the reduced average copper concentrations in drinking water by around 40% from 65 to 35 μg/L; the reduction is proportional to the phosphate dose. A corresponding 30% decrease in wastewater treatment work effluent concentrations is observed. No significant changes are evident in the zinc and nickel concentrations.